21. The null balance potentiometric measurement of voltage technique is not capable of measuring
DC voltage
AC voltage
Voltage with higher accuracy and sensitivity as compared to a deflection-type instrument
Dynamic and transient voltage changes
Answer.4. Dynamic and transient voltage changes
Explanation:
A potentiometer is an instrument designed to measure an unknown voltage by comparing it with a known voltage or standard voltage. It is also used for comparing the emf of two cells.
Characteristics of potentiometer:
As it measures the unknown voltage by comparing it with standard voltage rather than by actual deflection of the pointer. This ensures a high degree of accuracy.
The potentiometer measures the unknown voltage using null or balance conditions, hence no power is required for the measurement.
The determination of voltage using a potentiometer is quite independent of the source resistance.
It can be used to measure both DC and AC voltages.
It is not capable of measuring dynamic and transient voltage changes
22. A dc potentiometer is designed to measure up to about 2 V with a slide wire of 1600 m. The standard cell of emf 1.2 V balances at 1200mm. a test cell is seen to balance at 1400 mm. The emf of the test cell is
1.1 V
1.2 V
1.7 V
1.4 V
Answer.4. 1.4 V
Explanation:
Given-
E1 = 1.2 V
L1 = 1200 mm
L2 = 1400 mm
In a potentiometer
E ∝ L ∝ R
Where,
E = emf of the test cell
L = Balancing length of slide wire
R = Slide wire resistance
∴ E1/E2 = L1/L2
1.2/E2 = 1200/1400
E2 = 1.4V
23. The slide wire of a potentiometer should be ______ for much accurate results.
Thin but short
As long as possible
Very short
Thick
Answer.2. As long as possible
Explanation:
A potentiometer is defined as a 3 terminal variable resistor in which the resistance is manually varied to control the flow of electric current.
A potentiometer acts as an adjustable voltage divider
A potentiometer is a passive electronic component
Potentiometers work by varying the position of a sliding contact across a uniform resistance
The slide wire of the potentiometer to make it achieve high accuracy should be as long as possible.
24. The non-wire potentiometers are also called ______
Variable Potentiometer
Non-continuous Potentiometer
Continuous Potentiometer
None of the above
Answer.2. Non-continuous Potentiometer
Explanation:
The non-wire potentiometers are also called continuous potentiometers. As it consists of a continuous resistance element without any wire winding as such, its resolution is increased compared with the wire-wound potentiometer. The movement of the wiper is along a continuous surface and hence the wearing of body parts is considerably decreased.
25. The main materials used for non-wire or continuous potentiometers are
Metal Film
Carbon Film
Hot Moulded Carbon
All of the above
Answer.4. All of the above
Explanation:
The main materials used for non-wire or continuous potentiometers are as follows.
Thin Metal Film: In such type of potentiometer resistance element is formed by depositing a very thin layer of metal on proper insulating material like glass, ceramic, etc. The potentiometers with the thin metal film are less expensive and the change in resistance to environmental changes is very less. Moreover, such potentiometers can be used for d.c. as well as a.c. voltages.
Carbon Film: In a carbon film potentiometer, a thin film of carbon is deposited on & proper insulating material like glass, ceramic, etc. The advantages of carbon film potentiometers are low cost and low-temperature coefficient.
Hot Moulded Carbon: In such types of potentiometers, a resistance element is formed by molding a mixer of carbon and plastic. Such hot molded carbon potentiometers are most extensively used in a.c. application.
Cement: The resistance element is formed by fusing precious metal particles in the ceramic base. The main advantage of such potentiometers is their large power rating at high temperatures. They are also low-cost potentiometers with moderate temperatures.
26. Which of the following are characteristics of the Potentiometer?
Linearity
Resolution
Loading Effect
All of the above
Answer.4. All of the above
Explanation:
The main characteristics of Potentiometer are
Linearity
Loading effect
Loading error
Resolution
Linearity and sensitivity: We know that in order to achieve good linearity, the resistance. In order to get a high sensitivity, the output§ voltage should be high which in turn requires a high input voltage. Due to limitations of power dissipation, the input voltage is limited by the resistance of the potentiometer.
Resolution: Practically, the output voltage of the wire-wound potentiometric displacement transducer is not continuous for the given input with wiper movement but varies in steps giving a staircase waveform. The main reason for the non-continuous output is that the change in resistance between windings is not continuous with wiper movement.
27. The main advantages of the Potentiometer are
Simple in construction
High efficiency
Less expensive
All of the above
Answer.4. All of the above
Explanation:
Advantages of Potentiometers
It is simple in construction and operation.
It is having high electrical efficiency and provides sufficient output for further control operations.
It is very useful for displacement measurement of large amplitude.
It is best suited for measurements in the system with the least requirement.
It is not so much expensive.
28. The main drawback of the potentiometer is
Limited Resolution
High Noise
Mechanical Wear
All of the above
Answer.4. All of the above
Explanation:
Disadvantages of Potentiometer
In a linear potentiometer, a large force is required to move the wiper.
It has limited resolution and high electronic noise in the output.
Itis suffers from mechanical wear and misalignment of the wiper.
The output of the potentiometer is insensitive to the variations in the displacement of the wiper between two consecutive turns of wire.
29. The ohmic values of potentiometer ranges form
100 kΩ to 10 kΩ
200 kΩ to 50 kΩ
5 kΩ to 10 kΩ
1 kΩ to 2 kΩ
Answer.1. 100 kΩ to 10 kΩ
Explanation:
The power rating of potentiometer: The potentiometers are designed with a definite power rating which is related directly to their heat dissipating capacity. The manufacturers normally design a series of a potentiometer of a single turn with a diameter of 50 mm with a wide range of ohmic values ranging from 100 kΩ to 10 kΩ in steps of 100Ω.
30. The application of a potentiometer is
Used as a voltage divider
Audio control
Used as sensor
All of the above
Answer.4. All of the above
Explanation:
Application of Potentiometer
It can be used for measurement and control of large displacements of about 5 mm to 500 mm.
It can be used as an electric sensing element in pressure measurements, accelerometers, air crafts, etc.
It can also be used in hydraulic jacks for shaft position control, in pen recorders in servo balance position control, etc.
It has high signal output hence additional amplifier circuitry is not required to drive indicating or recording devices at the output.
The applications (uses) of the potentiometer:
Voltage divider: The potentiometer can be used as a voltage divider to change the output voltage of a voltage supply.
Audio control: Sliding potentiometers are commonly used in modem low-power audio systems as audio control devices. Both sliding (faders) and rotary potentiometers (knobs) are regularly used for frequency attenuation, loudness control, and for controlling different characteristics of audio signals.
Potentiometer as a sensor: lf the slider of the potentiometer is connected to the moving part of a machine, it can work as a motion sensor. A small displacement of the moving part causes a change in potential which is further amplified using an amplifier circuit. The potential difference is calibrated in terms of displacement of the moving part.
